[PATCH v2] mmc: dw_mmc: Reset DMA before enabling IDMAC

[Jaehoon Chung]

Hi, Sonny.

On 10/17/2014 01:58 AM, Sonny Rao wrote:
> We've already got a reset of DMA after it's done.  Add one before we
> start DMA too.  This fixes a data corruption on Rockchip SoCs which
> will get bad data when doing a DMA transfer after doing a PIO transfer.
> 
> We tested this on an Exynos 5800 with HS200 and didn't notice any
> difference in sequential read throughput.

Didn't affect the write throughput?
I tested this on exynos3/4 with DDR50 and HS200.

Acked-by: Jaehoon Chung <jh80.chung at samsung.com>
Tested-by: Jaehoon Chung <jh80.chung at samsung.com>

> 
> Signed-off-by: Sonny Rao <sonnyrao at chromium.org>
> Signed-off-by: Doug Anderson <dianders at chromium.org>
> Tested-by: Doug Anderson <dianders at chromium.org>
> ---
>  drivers/mmc/host/dw_mmc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 69f0cc6..ca67f69 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -83,6 +83,7 @@ struct idmac_desc {
>  #endif /* CONFIG_MMC_DW_IDMAC */
>  
>  static bool dw_mci_reset(struct dw_mci *host);
> +static bool dw_mci_ctrl_reset(struct dw_mci *host, u32 reset);
>  
>  #if defined(CONFIG_DEBUG_FS)
>  static int dw_mci_req_show(struct seq_file *s, void *v)
> @@ -448,6 +449,10 @@ static void dw_mci_idmac_start_dma(struct dw_mci *host, unsigned int sg_len)
>  
>  	dw_mci_translate_sglist(host, host->data, sg_len);
>  
> +	/* Make sure to reset DMA in case we did PIO before this */
> +	dw_mci_ctrl_reset(host, SDMMC_CTRL_DMA_RESET);
> +	dw_mci_idmac_reset(host);
> +
>  	/* Select IDMAC interface */
>  	temp = mci_readl(host, CTRL);
>  	temp |= SDMMC_CTRL_USE_IDMAC;
>